Showing papers in "Astrophysical Journal Supplement Series in 1988"

IRAS observations of galaxies in the Virgo cluster area

Abstract: IRAS data on 196 galaxies in the area of the Virgo Cluster are presented. The data derive from combining all available survey observations for each object and therefore achieve greater sensitivity than the IRAS Point Source Catalog (PSC). The enhanced sensitivity allows 78 galaxies to be detected at 12 microns, 82 at 25 microns, 139 at 60 microns, and 135 at 100 microns, compared to 16, 23, 88, and 95 detections listed in the PSC. From the blue compact dwarf galaxy sample, 23 and 19 objects are detected at 60 and 100 microns, compared to three and two detections listed in the PSC. The emission in three close pairs of galaxies which are reported as single sources in the PSC are separated here. These statistics demonstrate the importance and potential of a detailed examination of IRAS data, especially for possibly resolved sources and, in particular, for galaxies out to redshifts of 0.008 or galaxies with D(25) of 3 arcmin or greater.

A catalog of IRAS observations of large optical galaxies

Abstract: A catalog is presented of the IRAS observations of 85 galaxies listed in the Second Reference Catalogue of Bright Galaxies with blue-light isophotal diameters greater than 8'. “Total” flux densities at 12, 25, 60, and 100 µm, obtained from spatial maps constructed from co-added IRAS detector data, are reported. Infrared brightness profiles of the detected galaxies and infrared surface brightness contour maps of the galaxies for which structural features were resolved are displayed in an atlas. A far-infrared classification scheme based on the degree of central concentration and spatial structure of the 60 µm emission of the best-resolved galaxies is proposed. The 60 µm and blue-light isophotal diameters of the largest galaxies are compared.

C IV Absorption in a New Sample of 55 QSOs: Evolution and Clustering of the Heavy-Element Absorption Redshifts

Abstract: Les spectres optiques d'un echantillon complet de 55 quasars de redshifts compris entre 18 et 356 sont presentes pour le domaine compris entre la raie CIV 11549 d'emission et la foret Lyman α La liste des raies d'absorption est etablie pour chacun d'entre eux et les spectres sont discutes individuellement

Extended optical-line-emitting gas in radio galaxies: broad-band optical, narrow-band optical, and radio imaging of a representative sample

Abstract: A search for extended optical-line-emitting gas in a representative sample of power radio galaxies has been conducted in order to determine the frequency with which such gas is found in these galaxies and to assess the relationship of the gas to the radio source structure and the structure of the host galaxy. Contour maps and detailed descriptions are given for each source of the broad-band optical, narrow-band optical, and radio images obtained. From the images presented here, it is clear that extended optical-line-emitting is common in powerful radio galaxies. In some cases, the emission-line filaments appear to connect the host radio galaxy to an apparent companion galaxy. S-shaped regions of line emission are observed in five of the sources. Morphological peculiarities in the distribution of the optical continuum light from the host radio galaxy are also apparent in many of these sources. 109 references.

A statistical study of properties of Seyfert and starburst galaxies

Abstract: Spectral and morphological data for 282 Seyfert and emission-line galaxies spanning radio to X-ray wavelengths are compiled. The data include a large number of optical emission-line measurements which have not been reported previously. These data are intended to provide a convenient summary of the relevant properties of these galaxies, as well as a data base to search for correlations among the various parameters in order to obtain a better understanding of the active galaxy phenomenon. The paper presents the data and analyzes the distributions of various properties of Seyfert 1 and Seyfert 2 galaxies and starburst galaxies. It is found that Seyferts 2s have a higher 60 micron/forbidden O III 5007 A flux ratio than Seyfert 1s. This result, combined with the fact that Seyfert 2s are more heavily reddened, indicate that they have a higher dust content. It is also found that starburst nuclei are comparable to Seyfert 2s in far-infrared and 20 cm luminosities, although their optical spectra are markedly different.

A search for molecular outflows toward the pre-main-sequence objects

Abstract: A search for molecular outflows has been conducted toward a sample of 71 young stellar objects dominated by optically selected pre-main-sequence stars. Molecular outflows ranging in size from 0.07 to about 5 pc, with expansion velocities from 6 to 60 km/s, have been detected toward 20 of these objects and in an additional six infrared objects not included in the original survey. The apparent ages of the outflows are from 1000 to 500,000 yr; about half of the observed outflows are bipolar, with the rest showing a wide variety of morphologies. It is found that outflows driven by low-luminosity objects tend to be more bipolar than those driven by high-luminosity objects. The implications of the results of the study are discussed.

CO observations of all Virgo Cluster spiral galaxies brighter than BTo=12

Abstract: Presentation de donnees spectrales microondes a partir de l'observation de CO (J=1→0) a 115 GHz pour 42 galaxies de l'amas de la vierge. Les flux globaux, les distributions radiales, les diametres et les asymetries sont donnees pour chacune d'entre elles. On discute de la distribution moyenne de l'emission CO et de la possible interaction avec la matiere interstellaire. Les cartes radio de resolution 10 mK (T A ) sont aussi presentees

Uncertainties in 21 centimeter redshifts. I. Data

Abstract: High-precision data on the 21-cm redshifts, profile widths, and shapes for 625 galaxies are presented. Each galaxy is listed in a cross-identification and morphology table. High-resolution spectra are also given for each galaxy. Internal redshift consistency is roughly 1 km/s for galaxies for which the S/N is above 15. No systematic effects have been found which might influence the observed redshift quantization at 72.5 km/s or its submultiples. 8 references.

The orientations of the rotation axes of radio galaxies. II - Stellar rotation curves and velocity dispersion profiles

Abstract: The stellar kinematics of nearby, optically luminous, elliptical galaxies of moderate radio power is investigated to determine whether these galaxies are kinematically unusual or show evidence for a relationship between their radio properties and stellar dynamics. A model describing the structure and kinematics of elliptical galaxies is developed which allows for oblate, prolate, and triaxial figure types. The model is fitted to the data to estimate the position angle of the rotation axis and the scale and amplitude of the rotation curve for each galaxy. The results demonstrate that elliptical galaxies possess a wide range of rotation velocities and that the projected minor and rotation axes can be oriented very differently. There is a tendency for the rotation axis to align with one of the symmetry axes of the projected figure. 37 references.

Hydrogenic radiative recombination at low temperature and density

Abstract: The radiative recombination of hydrogenic ions is calculated in the limit of low density by the nl-method, extending the results of Pengelly (1964) to much lower temperatures (both case A and case B). A strong motivation is the detection of the emission-line spectrum of the old shell of Nova DQ Her 1934 reported by Williams et al. (1978), which revealed an electron temperature T(e) of about 500 K. The results are compared with the 1959 result of Seaton using the n-method, with those of Hummer and Storey (1987), which allow for the effects of collisions at finite density, and with the data for three cold old nova shells. Another motivation is the detection of relatively strong optical radiative recombination lines of C, N, and O in these shells. The abundances of these elements (recombining ions of charge Z) can be derived using a hydrogenic approximation to the effective radiative recombination coefficients, requiring the recombination coefficients of H(+) at even lower temperatures. 27 references.

A detailed study of the Lynds 1551 star formation region

Abstract: The results of an optical spectroscopic and photometric study of the star formation region Lynds 1551 and the young stellar object IRS 5 and a high-resolution spectroscopic study of the Herbig-Haro (HH) objects associated with the outflow from this region are reported. The results further establish IRS 5 as the source of the reflected light in the region. Spectral studies suggest that the spectrum of IRS 5 is dominated by the light from an accretion disk analogous to those characterizing objects of the rare class of FU Orionis objects. Analysis of high and medium resolution spectra of the optical jet emanating from IRS 5 strongly suggest that the jet HH objects are the bow shock interfaces between two winds coming from the IRS 5 region. The high-velocity wind is inferred to have a velocity of 440 km/s, and is identified as the stellar wind. High-density clumps in the stellar wind shock a lower-density, but much more pervasive second wind which has an inferred velocity of about 160 km/s. 69 references.

Performance Analysis of Direct N-Body Calculations

Abstract: A theoretical framework for analyzing the computational cost of gravitational N-body codes is introduced and applied to three different types of direct-summation codes, including the type of Aarseth code which has found most general use. The method of analysis, based on the probability distribution of nearest-neighbor distances, is described. The number of time steps required for a variety of different versions of the Aarseth scheme and a variety of physical models of spherical star clusters is estimated in order to measure the effects of different degrees of central concentration. Analytical estimates of computer time required are compared with actual measurements, and the validity of the scaling outside the range actually tested is discussed. A practical result for planning star cluster simulations on the next generation of supercomputers is derived. It is found that the consumption of computer time can be very centrally concentrated. 15 references.

The Structure and Dynamics of Ringed Galaxies. V. The Kinematics of NGC 1512, NGC 3351, NGC 4725, and NGC 4736

Abstract: The spirals NGC 1512, NGC 3351, NGC 4725, and NGC 4736 are four large nearby examples of ringed galaxies whose kinematic properties are studied in this paper by means of H-alpha Fabry-Perot interferometry Velocity fields are first analyzed in terms of pure circular motions, and approximate rotation curves and masses are derived Then, the kinematics of the inner rings alone are studied using a velocity-position angle diagram, and analyzed in terms of circular rotation, rotation plus uniform expansion or contraction, an unperturbed dispersion orbit, or a perturbed oval bar orbit The results show, first, that the inner ring in each of these galaxies is a region where H-alpha emission is enhanced compared with regions inside or outside the ring, and hence that the ring is a zone of active star formation Only for NGC 4725 does the velocity-position angle diagram of the inner ring show an unmistakable asymmetry indicative of significant noncircular motions However, for all four galaxies, models of stable elliptical orbits provide fits to the inner rings which are just as acceptable as pure rotation or expanding/contracting ring fits In no case is a unique kinematic model of the ring achievable, owing to inadequate knowledge of the parentmore » galaxy orientation parameters 55 references« less

A catalog of small, optically selected molecular clouds - Optical, infrared, and millimeter properties

Abstract: A catalog of 248 small molecular clouds selected from the northern hemisphere Palomar Observatory Sky Survey has been assembled. These clouds have angular sizes of less than 10 arcmin (the mean of the sample is 4 arcmin), are reasonably well-isolated, and centrally opaque. They most closely resemble small versions of the larger Bok globules and Barnard objects. Many (30%) of the smallest members of this catalog have not been previously cataloged or studied. Coordinates accurate to 0.5 arcmin, optical extents and orientation angles, and cross-references are given for all of the clouds. Radial velocities, obtained from CO observations, are listed for 158 of the clouds. Additionally, 339 associated or possibly associated IRAS point sources are listed for 147 of the clouds. As most of these clouds have few or no foreground stars and subtend small angular extents, they are likely the smallest (all < 1.5 pc) and simplest dark molecular clouds near the Sun. The mean ellipticity (b) of the clouds in the catalog is 2.0, indicating that spherical cloud models may not be appropriate for this sample. The mean orientations, with respect to the galactic plane, of the clouds showing ellipticities greater than unity has no angular dependence; that is, the local galactic plane does not seem to order the direction of the optically determined ellipticity for the clouds. The far-infrared properties of the clouds with associated IRAS sources are similar to those seen in the sample of dark cloud cores studied by Beichman et al. (1986) [Ap. J., 307, 337], but are somewhat cooler (19 K vs 28 K for the means) and less FIR bright. Millimeter 12CO (J = 2-1) observations of the centers of 93 of the cataloged clouds shows that most (70%) of the sample are cool (gas kinetic temperature ∼8 K) and quiescent (gas dynamical motions ≈ sonic). Some clouds exhibit warmer gas temperatures possibly driven by radiative heating from nearby stars. Another small group of clouds exhibit the cool temperatures and supersonic linewidths characteristic of active embedded protostellar collapse or outflow.

A Search List of Lines for Quasi-stellar Object Absorption Systems

Abstract: This paper lists the strongest atomic resonance lines longward of 912 A that are suitable for use in search lists for QSO absorption systems. The 179 lines have been selected according to the cosmic abundance of the element, the ionization potential of the atom, and the expected unsaturated equivalent width of the transition. Considerable effort has been directed toward quoting the most reliable wavelengths and oscillator strengths for each line. 71 references.

The laboratory millimeter- and submillimeter-wave spectrum of CH3OD

Abstract: The millimeter-wave and submillimeter-wave spectrum of CH3OD, a deuterated isotope of methanol known to be present in the interstellar medium, has been studied in the laboratory. Like all isotopes of methanol, CH3OD possesses a complex dense spectrum because of the phenomenon of internal rotation, sometimes referred to as torsional motion. Approximately 300 lines in the frequency range 130-700 GHz have been assigned. These lines involve transitions between rotational states with rotational quantum number J of not greater than 9 in both the A and the E substates of the lowest torsional state (v sub t = 0). The present data and previous data at lower frequencies (longer wavelengths) have been combined and analyzed by a procedure called the 'internal axis method'. The analysis yields spectral constants for CH3OD which, in turn, have been used to predict the frequencies of a number of other transitions of this species not measured in the laboratory.

Optical images of quasars and radio galaxies

Abstract: Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions. 12 references.

The velocity structure and turbulence at the center of the Orion Nebula

Abstract: Using the Coude Feed System of the Kitt Peak National Observatory at its highest possible dispersion and a CCD detector with wide dynamic range it was possible to examine in detail the radial and turbulent velocities of the Orion Nebula at the seeing limit. For the first time, multiple components of the spectral lines were resolved and the Gaussian profiles fit to them. Using four different observing runs, two circular areas 2 minutes in diameter were observed, the first centered on the theta sup 1 Orionis and the second centered on theta sup 2 Orionis. The velocity resolution of 1 km/s combined with the angular resolution of 2 seconds allowed observation in detail at line splitting as well as the location and measurement of high internal motions, about -50 km/s with respect to the bulk of ionized matter. Because over 900 different positions were measured, modern statistical techniques were used for the analysis of turbulence, so that the dispersion relation and the structure function could be calculated and compared with predictions of the Kolmogorov theory. The random motions showed correlation with spatial separation, as expected for turbulence; but comparison with predictions of the classical theory for nebular turbulence showed poormore » agreement. If Kolmogorov theory applies, then the energy must be input at many scales. 104 references.« less

Cyclotron line resonant transfer through neutron star atmospheres

Abstract: Monte Carlo methods are used to study in detail the resonant radiative transfer of cyclotron line photons with recoil through a purely scattering neutron star atmosphere for both the polarized and unpolarized cases. For each case, the number of scatters, the path length traveled, the escape frequency shift, the escape direction cosine, the emergent frequency spectra, and the angular distribution of escaping photons are investigated. In the polarized case, transfer is calculated using both the cold plasma e- and o-modes and the magnetic vacuum perpendicular and parallel modes.

Identifications and limited spectroscopy for Luyten common proper motion stars with probable white dwarf components. I - Pair brighter than 17th magnitude

Abstract: Identifications are provided for 103 bright Luyten common proper motion (CPM) stellar systems with m(pg) less than 17.0 mag containing likely white dwarf (WD) components. New spectral types are presented for 55 components, and spectral types for 51 more are available in the literature. With the CPM systems previously published by Giclas et al. (1978), the Luyten stars provide a uniform sample of nearly 200 pairs or multiples brighter than 17h magnitude. Selection effects biasing the combined samples are discussed; in particular, evidence is presented that fewer than 1 percent of wide WD binaries have been detected.

The Case low-dispersion northern sky survey. VII - Late-type stars

Abstract: Catalogue de 132 etoiles rouges faibles (magnitude rouge allant de 9 a 17) situees dans une zone d'environ 1000 degres carres dans la partie Nord des latitudes galactiques

Portrait of a novel nova: V1500 Cygni

Abstract: Etude de l'ejection et du reste de la nova V1500 Cygni 1975 d'apres toutes les observations acquises 3 ans apres le maximum lumineux

Cosmological Simulations Using the Hierarchical Tree Method

Abstract: Etude des proprietes de la methode en arbre hierarchique et de son efficacite a traiter le probleme a N corps dans l'agencement des galaxies en cosmologie

Redshifts of high-temperature emission lines in the far-ultraviolet spectra of late-type stars. II - New, precise measurements of dwarfs and giants

Abstract: Results are presented from an IUE SWP camera investigation of the occurrence of gasdynamic flows, analogous to the downdrafts of 10 to the 5th K material observed over magnetic active regions of the sun, among stars of late spectral type. The SWP calibration spectra study conducted documents the existence of local, small, persistent distortions of the echelle wavelength scales that are of unknown origin. Attention is given to the enormous widths of the stellar high-excitation emission lines in both the dwarfs and the giants, with respect to the comparatively small, subsonic Doppler shifts; the widths are typically an order of magnitude greater than the redshifts.

The Clark Lake 30.9 MHz galactic plane survey

Abstract: Cartographie a 30.9 MHz du plan galactique avec une resolution jamais atteinte a une frequence radio aussi basse (13'×11.1' au zenith). Une liste des radiosources recensees avec leur flux de densite et leur position est donnee

The ultraviolet spectrum of noncoronal late-type stars: the gamma Crucis (M3.4 III) reference spectrum

Abstract: A guide is presented to the UV spectrum of M-type giants and supergiants whose outer atmospheres contain warm chromospheres but not coronae. The M3 giant Gamma Crucis is taken as the archetype of the cooler, oxygen-rich, noncoronal stars. Line identifications and integrated line flux measurements of the chromospheric emission features seen in the 1200-3200 A range of IUE high-resolution spectra are presented. The major fluorescence processes operating in the outer atmosphere of Gamma Crucis, including eight previously unknown pumping processes and 21 new fluorescent line products, are summarized, and the enhancements of selected line strengths by 'line leakage' is discussed. A set of absorption features toward the longer wavelength end of this range is identified which can be used to characterize the radial velocity of the stellar photospheres. The applicability of the results to the spectra of noncoronal stars with different effective temperatures and gravities is discussed.

Photometric Variability in Chromospherically Active Stars. II. The Rapidly Rotating Single Stars

Abstract: Observations UBV de 5 etoiles en rotation rapide a l'aide d'un telescope entierement automatique